The invention relates to the growth of photosynthetic organisms such as microorganisms, algae, photosynthetic bacteria, photosynthetic organisms and animal symbionts; higher plant tissues, and the like.
It is one object of the invention to provide apparatus and method for the purpose specified which is particularly simple and efficient and offers other advantages.
GB-A-2118572 discloses a photosynthetic bioreactor comprising a sinuous transparent tube having a pump arranged to pump liquid culture through the tube at a ate such that a Reynolds number of 2,000 or greater is achieved. This is to ensure turbulence sufficient to ensure that all cells of the culture are frequently exposed to radiation.
U.S. Pat. No. 4,473,970 discloses an upright tubular bioreactor through which CO2 and O2 are pumped, above a liquid culture medium which is subjected to continuous agitation by being pumped. Transverse baffles are located in the gas flow path.
U.S. Pat. No. 5,242,827 discloses a tubular bioreactor and teaches that it is known to include circulating plastics balls in such reactors in order to ensure an agitation of the nutrient medium and cleaning of the tubes as a result of the balls rubbing on their walls. Means for the introduction and removal of the balls and for stopping their flow are disclosed.
WO-A-94/09113 discloses a tubular photobioreactor having a rectangular bore and a xe2x80x9cringxe2x80x9d of rectangular cross-section which is forced through the tube for scraping its inner walls.
In one aspect the invention provides apparatus for use in growing cultures of photosynthetic organisms, the apparatus comprising a bath containing liquid, at least one elongate passageway having a gas inlet towards one end and a gas outlet towards the other; and means adapted to wipe the inside surface of the passageway; the passageway being located within the liquid at an inclination to the horizontal with a gas inlet being lowermost.
Preferably the wiping means is a rotary wiping means, preferably having a rotary axis which is substantially parallel to the longitudinal axis of the passageway.
Preferably the means for wiping the inside of the passageway is a rotor having vanes and extending the length of the passageway; and a motor or the like being present for rotating the rotor.
The passageway is suitably made of a material which is substantially transparent to visible radiation such as glass or polycarbonate. The passageway may optionally be made of an opaque material, e.g. where a dark stage is required. If appropriate the passageway may have a covering or the wall material may include photo adjusting compounds.
Preferably the passageway is disposed at an angle to the horizontal ranging from substantially vertical to say 30xc2x0 or 40xc2x0 to the horizontal.
Preferably the passageway is generally circular in cross-section.
The bath may for example, take the form of a lagoon, pond or the like. Preferably the bath contains water as the liquid. To enhance the photosynthetic and heating effect preferably the wall of the bath has light reflective surfaces above and/or below the level of the liquid. Dyes or fluorescent agents may optionally be present in the water to selectively remove visible, UV or IR radiation or enhance it as in fluorescence. Where the bath is located outside a building preferably means are present to reduce heat loss at night and/or to cause cooling during the day, whereby to maintain the temperature of the liquid substantially constant. Such means may for example, be a cover (which may be an integral sheet or say floating balls of polystyrene) to insulate or a fountain to circulate the water to cool it by enhanced evaporation.
In another aspect the invention provides apparatus for use in the culture of photosensitive organisms, comprising a pond or lagoon containing water, elongate containers of the organisms being present in the water, and the containers being disposed at an inclination to the horizontal.
In another aspect the invention provides an assembly comprising a plurality of passageways as defined, arranged generally parallel to each other, the passageways being free of the gas inlet and outlet, neighbouring passageways communicating through a hollow bridging element which includes the gas inlet and the gas outlet.
In yet another aspect the invention provides a method of growing a culture of micro-organisms comprising passing a culture liquid through apparatus or the assembly as defined and supplying to the gas inlet CO2 gas and/or other gases which may aid growth or constituent balance of specific organisms. Oxygen or like gases are released via the outlet and may be collected. The liquid may be passed continuously or in a batch mode.
A wide variety of micro organisms may be treated in the apparatus of the invention. Examples include microalgae, macroalgae tissue, photosynthetic bacteria, photosynthetic archaebacteria, heterotophic bacteria fungi, plant tissue culture, water fleas; and the like. Apparatus of the invention may be used in the culture of micro-organisms for the production of colourings and anti-oxidants, fishfeeds, pharmaceuticals and the like.
Apparatus of the invention is able to maintain continuously growing cultures of Haematococcus for several months to provide commercial harvests of Astaxanthin. Apparatus of the invention can be used for the culture of strains of Dunaliella, a unicellular, flagellated green algae without a cell wall which contain high concentration (up to 10%) of beta-carotene when growing under high light intensities and high salinities (100 g/l). Beta-carotene has traditionally been used as a food colouring agent and may have medical uses. One major benefit of the apparatus of the invention is purity of the products. Although several companies grow Dunaliella in open ponds, product contamination regularly occurs. Apparatus of the invention is able to maintain continuously growing contaminant-free cultures of Dunaliella resulting in high purity beta-carotene.
Apparatus of the invention can be used to produce live feeds, on site, or dried and processed algae based feeds that are shipped to users.
Micro algae cultivated in the apparatus of the invention provide the most effective biological means known to remove carbon dioxide from the atmosphere. At the same time, the biomass they produce an be used as fuel.
Micro algae can remove carbon dioxide from the atmosphere 25 times faster than the fastest growing trees. Carbon dioxide is removed from stack gases before it even enters the atmosphere. Trees, on the other hand, remove carbon dioxide after it enters the earth""s atmosphere. Biomass from micro algae can be used as a fuel. Micro algae produced at the site of a fossil fuel burning plant could be directly fed into the fuel combustion process.
Micro algae cultivated in accordance with the invention can supply quantities adequate for all purposes ranging from screening to production.
Apparatus of the invention may also be used in the treatment of gases.
Further preferred features are defined in the dependent claims.